The disclosure of Japanese Patent Application No. 11-168519 filed on Jun. 15, 1999 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The present invention relates to a control apparatus and method of an internal combustion engine installed on a motor vehicle, and in particular to a control apparatus and method of a vehicle engine that controls the ignition timing so as to reduce vibration upon acceleration of the motor vehicle.
2. Description of Related Art
In internal combustion engines installed on motor vehicles, when a throttle valve is opened by a large degree in response to depression of an accelerator pedal, for example, and a torque generated by the engine is rapidly increased, xe2x80x9ctorsional strainxe2x80x9d arises in a power transmitting system through which the output of the engine is transmitted to the drive wheels of the vehicle. As a result, xe2x80x9ctorsional vibrationxe2x80x9d occurs in the power transmitting system, due to a restoring force against the torsional strain. Immediately after the engine is brought into an acceleration operating state as a result of a change in the opening amount of the throttle valve, therefore, the acceleration varies or fluctuates in the longitudinal direction of the vehicle due to the torsional vibration. Such acceleration fluctuations at the time of acceleration of the vehicle cause vibration (vibration upon acceleration), or so-called xe2x80x9ctransient surgexe2x80x9d or xe2x80x9csurgingxe2x80x9d, to occur in the longitudinal direction of the vehicle, which may deteriorate the driveability.
In order to alleviate or reduce the vibration upon acceleration as described above, it is known to control the ignition timing so as to vary the torque generated by the engine as needed in accordance with acceleration fluctuations at the time of acceleration of the vehicle (as disclosed in Japanese Laid-open Patent Publication No. 5-321803). FIG. 9 shows a method of controlling an internal combustion engine installed on a motor vehicle, in which such ignition timing control is performed.
When the flow rate of intake air introduced into the engine is increased (i.e., when the engine is brought into an acceleration operating state) as a result of an increase in the opening amount of a throttle valve (throttle opening amount) as shown in FIG. 9, torsional strain due to a rapid increase in the torque generated by the engine arises in the power transmitting system. As a result, the acceleration as measured in the longitudinal direction or running direction of the vehicle fluctuates as indicated by a broken line in the second graph of FIG. 9, and vibration upon acceleration occurs.
In the situation as described above, the control apparatus is adapted to control the ignition timing so that the phase of the torque generated by the engine is reversed relative to (or made opposite to) the phase of the vibration as the engine proceeds to the acceleration state. More specifically, during a period of time in which the acceleration varies to the front of the vehicle in the running direction of the vehicle, the ignition timing is delayed or lagged by reducing the ignition efficiency of the engine. During a period in which the acceleration varies to the rear of the vehicle in the vehicle running direction, the ignition timing is advanced so as to resume the ignition efficiency that has been reduced.
The graph of FIG. 9 labeled as xe2x80x9cGenerated Torquexe2x80x9d indicates changes in the normally or naturally generated torque (broken line) when no particular control is performed, and changes in the generated torque (solid line) when the above-described control is performed. With the ignition timing controlled in the above manner, the torque generated by the engine as indicated by the solid line is reduced as compared with the normally generated torque, during a period in which the acceleration varies forward in the running direction of the vehicle, and returns to the original or normal level (broken line) during a period in which the acceleration varies rearward in the running direction of the vehicle. As a result, the fluctuations in the acceleration of the vehicle change as indicated by a solid line in the second graph of FIG. 9, and the amplitude of the fluctuations is reduced as compared with that of the fluctuations as indicated by a broken line. Consequently, the vibration upon acceleration can be reduced.
A system that variably controls the torque generated by the engine as described above utilizing control of the ignition timing at the time of acceleration of the vehicle, has a limit in the effect of reducing the vibration upon acceleration.
In the method as described above, the torque generated by the engine can be reduced with a certain degree of freedom by controlling the ignition timing, and therefore forward or positive variations in the acceleration in the running direction of the vehicle can be effectively reduced. The upper limit of the generated torque of the engine is determined by the flow rate of intake air introduced into the engine at this time. Accordingly, there is a limit to the amount of an increase in the generated torque when reducing rearward or negative variations in the acceleration in the running direction of the vehicle. It is also to be noted that the ignition timing during engine operations is generally set to such a phase that provides the highest ignition efficiency, so as to ensure a sufficiently high output efficiency of the engine. Thus, the generated torque cannot be increased to be larger than the normally generated torque, even if an attempt is made to increase the generated torque.
Also, the average value of the generated torque during the above-described variable torque control is reduced as compared with the average value of the normally generated torque. Accordingly, the acceleration performance of the vehicle may deteriorate during the variable torque control.
The present invention has been developed in light of the above-described situations. It is therefore an object of the invention to provide a control apparatus of an internal combustion engine that is able to effectively suppress vibration upon acceleration of the vehicle that occurs due to an increase in the torque generated by the engine when it is in an acceleration operating state.
To accomplish the above and/or other objects, one aspect of the invention provides a control apparatus of an internal combustion engine installed on a motor vehicle, which includes a controller. The controller determines when the engine is in an acceleration operating state in which vibration occurs. The controller also controls the output of the engine when the engine is determined to be in the acceleration operating state in a manner so as to reduce the vibration. During a period of time in which the engine is determined to be in the acceleration operating state, the controller controls an opening amount of a throttle valve provided in the engine so that the opening amount is set to a second opening amount that is larger than a first opening amount to which the opening amount would be set if the controller had not determined that the engine was in the acceleration operating state.
In the control apparatus constructed as described above, when the accelerator pedal is pressed down, and the engine is brought into an acceleration operating state, and the controller detects vibration upon acceleration that occurs due to torsional vibration of a power transmitting system of the vehicle resulting from an increase in the torque generated by the engine. During a certain period in which the vibration upon acceleration occurs, the opening amount of the throttle valve is controlled to the second opening amount that is larger than the first opening amount that is originally determined depending upon the operating state of the engine. As a result, the flow rate or specific volume of intake air introduced into the engine is increased, and the generated torque of the engine is allowed to be increased.
The above arrangement makes it possible to suppress the vibration upon acceleration of the vehicle that occurs due to an increase in the generated torque when the engine is in an acceleration operating state.
With the torque generated by the engine thus allowed to be increased, the average of the generated torque can be held at a high level, and therefore the acceleration performance of the vehicle can be maintained at a high level.
The controller may control the output of the engine so as to reduce the vibration.
In the control apparatus as described above, the controller preferably may gradually reduce the opening amount of the throttle valve from the second opening amount toward the first opening amount while the engine is determined to be in the acceleration operating state.
In the form of the invention as described just above, the rate or degree of an increase in the generated torque under the above-described control (variable torque control) is reduced as the vibration upon acceleration fades away. Accordingly, the control of varying the torque generated by the engine can be smoothly and appropriately followed by normal control.